Microflotation and surface chemical studies were conducted on chromite, and some of the minerals usually associated with such chromites, from the Stillwater Complex, Montana Considering the chromite, it was found that aging the ground mineral in air or heating it markedly affected its flotation behavior. Much of the effects could be attributed to oxidation reactions involving surface chromium and iron species. Strongly acid pretreating the mineral appeared to reverse these effects. It can be concluded that the manner in which the mineral (or ore) is pretreated is of utmost importance in its flotation. Work carried out on associated gangue minerals determined how the minerals are likely to behave in a flotation environment and how certain foreign ions derived from chromite ore can affect the surface characteristics of the ions and presumably their behavior in a flotation circuit.